Add toggle functionality for top stack bar visibility and persistent button to reveal it

dicom-viewer/src/App.tsx

@@ -173,6 +173,8 @@ function App({ container_id, imageStacks, autoCacheStack, annotationJson, viewer
   const [presetsOpen, setPresetsOpen] = useState(false);
 
   const [settingsOpen, setSettingsOpen] = useState(false);
+  // Control visibility of the global top stack bar (hidden by default)
+  const [topBarVisible, setTopBarVisible] = useState(false);
 
   const [fullscreenHoverIdx, setFullscreenHoverIdx] = useState<number | null>(null);
   const [openDropdownIdx, setOpenDropdownIdx] = useState<number | null>(null);
@@ -2983,7 +2985,25 @@ function App({ container_id, imageStacks, autoCacheStack, annotationJson, viewer
         </div>
       )}
 
-      {/* Top bar stack browser */}
+      {/* Top bar stack browser (hidden by default) */}
+      <div style={{ display: "flex", alignItems: "center", gap: 12, marginBottom: 8 }}>
+        <button
+          onClick={() => setTopBarVisible(v => !v)}
+          style={{
+            background: topBarVisible ? "#1976d2" : "#333",
+            color: "#fff",
+            border: "none",
+            padding: "8px 12px",
+            borderRadius: 4,
+            cursor: "pointer",
+          }}
+          aria-pressed={topBarVisible}
+          aria-label={topBarVisible ? "Hide stack bar" : "Show stack bar"}
+        >
+          {topBarVisible ? "Hide Stack Bar" : "Show Stack Bar"}
+        </button>
+
+        {topBarVisible && (
           <div
             style={{
               position: "absolute",
@@ -3064,6 +3084,28 @@ function App({ container_id, imageStacks, autoCacheStack, annotationJson, viewer
           ));
         })()}
           </div>
+        )}
+      </div>
+      {/* Persistent floating button to reveal the stack bar */}
+      <button
+        onClick={() => setTopBarVisible(true)}
+        style={{
+          position: "absolute",
+          top: 12,
+          left: 12,
+          zIndex: 2000,
+          background: "#1976d2",
+          color: "#fff",
+          border: "none",
+          padding: "8px 10px",
+          borderRadius: 6,
+          cursor: "pointer",
+          boxShadow: "0 2px 10px rgba(0,0,0,0.3)",
+        }}
+        aria-label="Show stack bar"
+      >
+        Show Stacks
+      </button>
 
   <div>
         {/* Side menu toggle button */}